With the start of spring comes the melting of snow and arrival of standing water or floods. Here’s a look at what trees are tolerant and intolerant of flooding.

Flooding is a fairly common occurrence in Michigan, especially in the spring when snow melt is accompanied by rain, and later in the year following heavy thunderstorms. After a flood, we frequently receive phone calls from homeowners wondering how long their trees can survive being underwater. As with most things, the answer is “It depends.”

For the most part, short-term flooding (two or three days) should not cause too many issues with trees. Trees that are flooded when they are still dormant will be less effected by flooding than if the inundation occurred during the middle of the growing season. The type of tree also makes a huge difference in its ability to survive flooding. Many tree species can survive months under water while others may be killed by just a few days of inundation.

In general, a species’ native habitat can give us a pretty good clue as to how well it can recover from flooding. Upland species, such as hickory and many oaks, usually do not survive flooding while bottomland species, like red maple or sweetgum, are more tolerant of flooding. Most evergreen conifers are relatively intolerant of flooding. Exceptions are white spruce and arborvitae, which can tolerate some flooding. Also, deciduous conifers (larch, baldcypress and dawn redwood) are usually very tolerant of flooding. Flood tolerance ratings of trees can sometimes be confusing, and species listed as tolerant on one list may be listed as intolerant on another.

The table presented below is excerpted from one of the most comprehensive reviews of flood tolerance in trees and provides a good reference. As you’ll note in the table, green and white ash were among the most flood tolerant of our common landscape trees. Understanding the relative flood tolerance of trees will be increasingly important as we think about replacement species for ash.

Relative tolerance of trees and shrubs to flooding during the growing season (Source: Whitlow and Harris 1979)

Species

Common Name

Very Tolerant¹

Tolerant ²

Somewhat Tolerant³

Intolerant4

Acer negundo

Boxelder

X

X

Acer rubrum

Red maple

X

Betula nigra

River birch

X

Carya ovata

Shagbark hickory

X

Celtis occidentalis

Hackberry

X

Cephalanthus occidentalis

Buttonbush

X

Cereis canadensis

Redbud

X

Cornus florida

Flowering dogwood

X

Crataegus mollis

Downey hawthorn

X

Fraxinus americana

White ash

X

Fraxinus pennsylvanica

green ash

X

X

Gleditsia triacanthos

Honeylocust

X

Gymnocladus dioicus

Kentucky coffeetree

X

Juglans nigra

Black walnut

X

Liquidambar styraeiflua

Sweetgum

X

Nyssa sylvatica

Blackgum

X

Platanus occidentalis

Sycamore

X

X

Populus deltoides

Eastern cottonwood

X

Prunus serotina

Black cherry

X

Quercus alba

White oak

X

Quercus bicolor

Swamp white oak

X

Quercus imbricaria

Shingle oak

X

Qucrcus macrocarpa

Bur oak

X

Quercus palustris

Pin oak

X

Quercus rubra

Red oak

X

Salix nigra

Black willow

X

Sassafras albidum

Sassafras

X

Taxodium distichum

Baldcypress

X

Ulmus americana

American elm

X

Ulmus rubra

Red elm

X

1 Very Tolerant: Able to survive deep, prolonged flooding for more than 1 year. 2 Tolerant: Able to survive deep flooding for one growing season, with significant mortality occurring if flooding is repeated the following year. 3 Somewhat Tolerant: Able to survive flooding or saturated soils for 30 consecutive days during the growing season. 4 Intolerant: Unable to survive more than a few days of flooding during the growing season without significant mortality.